Search for Excited Muons Decaying Via a Contact Interactino in Proton-proton Collisions at & Radic ; S PDF Download

Author: Glenn Oliver Amundsen
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Category : Colliders (Nuclear physics)
Languages : en
Pages : 137

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Languages : en
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In this study, a new search signature for excited leptons is explored. Excited muons are sought in the channel ${pp}\to \mu {\mu }^{* }\to \mu \mu \ {\rm{jet}}\;{\rm{jet}}$, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb-1 of pp collision data at a centre-of-mass energy of $\sqrt{s}\;=\;8\;{\rm{TeV}}$ taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass ${m}_{{\mu }^{* }}$. For ${m}_{{\mu }^{* }}$ between 1.3 and 3.0 TeV, the upper limit on $\sigma B({\mu }^{* }\to \mu q\bar{q}$) is between 0.6 and 1 fb. Limits on $\sigma B$ are converted to lower bounds on the compositeness scale [Lambda]. In the limiting case ${\rm{\Lambda }}={m}_{{\mu }^{* }}$, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger ${\mu }^{* }$ masses improve upon previous limits from traditional searches based on the gauge-mediated decay ${\mu }^{* }\to \mu \gamma $.

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Languages : en
Pages : 8

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We present the results of a search for the production of an excited state of the muon, [mu]*, in proton antiproton collisions at √s = 1.96 TeV. The data have been collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 380 pb−1. We search for [mu]* in the process p{bar p} → [mu]*[nu], with the [mu]* subsequently decaying to a muon plus photon. No excess above the standard model expectation is observed in data. Interpreting our data in the context of a model that describes [mu]* production by four-fermion contact interactions and [mu]* decay via electroweak processes, we exclude production cross sections higher than 0.057 pb-0.112 pb at the 95% confidence level, depending on the mass of the excited muon. Choosing the scale for contact interactions to be [Lambda] = 1 TeV, excited muon masses below 618 GeV are excluded.

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Languages : en
Pages : 8

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We present the results of a search for the production of an excited state of the muon,?*, in proton antiproton collisions at √s = 1.96 TeV. The data have been collected with the D0 experiment at the Fermilab Tevatron Collider and correspond to an integrated luminosity of approximately 380 pb−1. We search for?* in the process p{bar p} →?*?, with the?* subsequently decaying to a muon plus photon. No excess above the standard model expectation is observed in data. Interpreting our data in the context of a model that describes?* production by four-fermion contact interactions and?* decay via electroweak processes, we exclude production cross sections higher than 0.057 pb-0.112 pb at the 95% confidence level, depending on the mass of the excited muon. Choosing the scale for contact interactions to be? = 1 TeV, excited muon masses below 618 GeV are excluded.

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Languages : en
Pages : 7

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The authors present a search for excited and exotic muon states [mu]*, conducted using an integrated luminosity of 371 pb−1 of data collected in p{bar p} collisions at √s = 1.96 TeV at the Tevatron with the CDF II detector. They search for associated production of [mu][mu]* followed by the decay [mu]* → [mu][gamma], resulting in the [mu][mu][gamma] final state. They compare the data to model predictions as a function of the mass of the excited muon M{sub [mu]*}, the compositeness energy scale [Lambda], and the gauge coupling factor f. No signal above the standard model expectation is observed in the [mu][gamma] mass spectrum. In the contact interaction model, they exclude 107

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Category :
Languages : en
Pages : 7

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Book Description
The authors present a search for excited and exotic muon states?*, conducted using an integrated luminosity of 371 pb−1 of data collected in p{bar p} collisions at √s = 1.96 TeV at the Tevatron with the CDF II detector. They search for associated production of??* followed by the decay?* →??, resulting in the??? final state. They compare the data to model predictions as a function of the mass of the excited muon M{sub?*}, the compositeness energy scale?, and the gauge coupling factor f. No signal above the standard model expectation is observed in the?? mass spectrum. In the contact interaction model, they exclude 107

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Languages : en
Pages : 22

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A search is performed in proton–proton collisions at √s=8 TeV for exotic particles decaying via WZ to fully leptonic final states with electrons, muons, and neutrinos. The data set corresponds to an integrated luminosity of 19.5 fb-1. No significant excess is observed above the expected standard model background. Upper bounds at 95% confidence level are set on the production cross section of a W' boson as predicted by an extended gauge model, and on the W'WZ coupling. The expected and observed mass limits for a W' boson, as predicted by this model, are 1.55 and 1.47 TeV, respectively. Stringent limits are also set in the context of low-scale technicolor models under a range of assumptions for the model parameters.

Author: Preema R. Pais
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Category :
Languages : en
Pages :

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Many new physics models predict the existence of neutral, weakly interacting, long-lived particles that can decay within the detector volume, producing a distinctive experimental signature. A search is performed for a pair of such particles, using proton-proton collision data at √s = 8 TeV collected by the ATLAS detector in 2012, corresponding to a total integrated luminosity of 20.3 fb-1. Novel techniques are developed for the reconstruction of displaced decays to hadronic jets in the inner tracking detector and muon spectrometer. No significant deviation is found from the number of background events expected from Standard Model processes. The data are interpreted in terms of Hidden Valley scenarios with a Z' boson mediator. This dissertation presents the first results for a heavy Z' boson decaying to displaced hadronic jets.

Author: Bryan Cardwell
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ISBN:
Category : Leptons (Nuclear physics)
Languages : en
Pages : 0

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A search is presented for new long-lived particles that propagate a measurable distance through the CMS detector before decaying to leptons. The search is performed in 113–118 fb-1 of proton-proton collision data produced by the CERN LHC at a center-of-mass energy of 13 TeV and collected by the CMS detector in 2016, 2017, and 2018. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10 cm. Using transverse impact parameter as the discriminating variable allows for sensitivity to displaced decays without requiring that the leptons form a common vertex. The search is designed to be sensitive to a wide range of new physics models that produce displaced di-lepton final states. The observation is consistent with the background-only hypothesis, and limits are set on the product of the cross-section of top squark pair production and the branching fraction to a lepton and a b or d quark through an R-parity-violating vertex. For a proper decay length hypothesis of 2 cm, top squarks with masses up 1500 GeV are excluded at the 95% confidence level.

Author: Weifeng Ji
Publisher:
ISBN:
Category : Large Hadron Collider (France and Switzerland)
Languages : en
Pages : 112

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In this dissertation, I present the searches looking for decays of stopped massive long-lived exotic particles, which are pair produced in the proton-proton collisions at 13 TeV and come to rest afterwards in the CMS detector at the CERN LHC. The decays are most likely to be observed when there are no collisions. Two specific decay scenarios are studied: a long-lived particle (LLP) decaying hadronically or semi- leptonically in the calorimeter, and a LLP decaying semi-leptonically or leptonically to a pair of muons in the muon detector. The calorimeter-based search is performed using 2.7 fb-1 of 13 TeV collision run data collected in 2015 and 35.9 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 721 hours. The muon search is performed using 2.8 fb-1 of 13 TeV collision run data collected in 2015 and 36.2 fb-1 of 13 TeV collision run data collected in 2016, corresponding to a total trigger livetime of 744 hours. Search results are interpreted in a couple of simplified models. The limits on the production cross sections and masses of LLPs are calculated as a function of particle lifetimes, which vary from 100 ns to 10 days, assuming the corresponding decaying branching fractions to be 100%. The results are the most stringent ones on the stopped LLPs so far.